Auto merge of rust-lang#119528 - wesleywiser:revert_117472, r=nnethercote

[beta] Revert rust-lang#117472: Stabilize C string literals

Based on discussion in [#t-lang](https://rust-lang.zulipchat.com/#narrow/stream/213817-t-lang/topic/rfc.203349.3A.20mixed.20utf8.20literals), revert the stabilization of C string literals in Rust 1.76.

I also reverted rust-lang#118566 as it uses the newly stabilized C string literals in various places.

Author: bors

compiler/rustc_ast_passes/src/feature_gate.rs

@@ -515,6 +515,7 @@ pub fn check_crate(krate: &ast::Crate, sess: &Session, features: &Features) {
             }
         };
     }
+    gate_all!(c_str_literals, "`c\"..\"` literals are experimental");
     gate_all!(
         if_let_guard,
         "`if let` guards are experimental",

compiler/rustc_builtin_macros/src/concat_bytes.rs

@@ -19,8 +19,8 @@ fn invalid_type_err(
     let snippet = cx.sess.source_map().span_to_snippet(span).ok();
     match ast::LitKind::from_token_lit(token_lit) {
         Ok(ast::LitKind::CStr(_, _)) => {
-            // Avoid ambiguity in handling of terminal `NUL` by refusing to
-            // concatenate C string literals as bytes.
+            // FIXME(c_str_literals): should concatenation of C string literals
+            // include the null bytes in the end?
             cx.emit_err(errors::ConcatCStrLit { span: span });
         }
         Ok(ast::LitKind::Char(_)) => {

compiler/rustc_codegen_llvm/src/lib.rs

@@ -8,7 +8,7 @@
 #![feature(rustdoc_internals)]
 #![doc(rust_logo)]
 #![doc(html_root_url = "https://doc.rust-lang.org/nightly/nightly-rustc/")]
-#![cfg_attr(bootstrap, feature(c_str_literals))]
+#![feature(c_str_literals)]
 #![feature(exact_size_is_empty)]
 #![feature(extern_types)]
 #![feature(hash_raw_entry)]

compiler/rustc_feature/src/accepted.rs

@@ -76,8 +76,6 @@ declare_features! (
     (accepted, bindings_after_at, "1.56.0", Some(65490)),
     /// Allows empty structs and enum variants with braces.
     (accepted, braced_empty_structs, "1.8.0", Some(29720)),
-    /// Allows `c"foo"` literals.
-    (accepted, c_str_literals, "1.76.0", Some(105723)),
     /// Allows `#[cfg_attr(predicate, multiple, attributes, here)]`.
     (accepted, cfg_attr_multi, "1.33.0", Some(54881)),
     /// Allows the use of `#[cfg(doctest)]`, set when rustdoc is collecting doctests.

compiler/rustc_feature/src/unstable.rs

@@ -359,6 +359,8 @@ declare_features! (
     (unstable, async_fn_track_caller, "1.73.0", Some(110011)),
     /// Allows builtin # foo() syntax
     (unstable, builtin_syntax, "1.71.0", Some(110680)),
+    /// Allows `c"foo"` literals.
+    (unstable, c_str_literals, "1.71.0", Some(105723)),
     /// Treat `extern "C"` function as nounwind.
     (unstable, c_unwind, "1.52.0", Some(74990)),
     /// Allows using C-variadics.

compiler/rustc_parse/src/lexer/mod.rs

@@ -223,6 +223,9 @@ impl<'a> StringReader<'a> {
                 rustc_lexer::TokenKind::Literal { kind, suffix_start } => {
                     let suffix_start = start + BytePos(suffix_start);
                     let (kind, symbol) = self.cook_lexer_literal(start, suffix_start, kind);
+                    if let token::LitKind::CStr | token::LitKind::CStrRaw(_) = kind {
+                        self.sess.gated_spans.gate(sym::c_str_literals, self.mk_sp(start, self.pos));
+                    }
                     let suffix = if suffix_start < self.pos {
                         let string = self.str_from(suffix_start);
                         if string == "_" {

library/std/src/lib.rs

@@ -308,7 +308,7 @@
 //
 // Library features (core):
 // tidy-alphabetical-start
-#![cfg_attr(bootstrap, feature(c_str_literals))]
+#![feature(c_str_literals)]
 #![feature(char_internals)]
 #![feature(core_intrinsics)]
 #![feature(core_io_borrowed_buf)]

src/doc/edition-guide

@@ -1,5 +1,6 @@
 #![allow(clippy::needless_raw_string_hashes, clippy::no_effect, unused)]
 #![warn(clippy::needless_raw_strings)]
+#![feature(c_str_literals)]
 
 fn main() {
     "aaa";